The Missoula City-County Health Department is asking for the public’s help in locating the source of a bad smell that has been occurring randomly in Missoula since the beginning of the year.

"We still don't know the source of the smell, that appears to be in a rather concentrated area on the westside and the northside," said health department administrator Ellen Leahy. "Other agencies, for example, Missoula city fire were called in many times because the odor actually smells like natural gas. Northwest Energy has also been called, and they have repeatedly been able to rule out natural gas."

The smell is reportedly very similar to mercaptan, the pungent, but not-harmful ingredient added to natural gas so that it can be detected before an explosion. Leahy says the only thing the city knows for sure is that the smell is not caused by natural gas.

"In terms of an explosive risk, that has been ruled out, however that leaves us without knowing what it is. If we could identify the location that the source is coming from, perhaps we could identify what the substance is, but it has been so ephemeral we can't do that either."